Cypress S6J3200 Series, Manual

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CHAPTER 31:Memory Protection Unit for AXI
S6J3200 Series Hardware Manual Document Number: 002-04852 Rev. *G 1159
5.
Notes on Using MPU AXI
This section is the "programmer’s guide", which lists the usage notes for programming the MPU AXI
module. It is recommended to read these guidelines before programming the MPU AXI module.

General Usage Notes
−
Reserved bits return undefined values. The software programs shall be independent of the values
read from the reserved register bits
−
The MPU AXI supports storage of information of first memory protection violation on the bus.
Therefore, once an NMI interrupt flag is set, the further monitoring of AXI master interface is stalled
until MPUXn_CTRL0:NMI bit is cleared. This implies that any protection violation occurring on the
bus while the MPUXn_CTRL0:NMI is set are simply ignored by MPU AXI. Software developers
must therefore try to keep the ISR size small, so that the NMI interrupt of MPU AXI does not remain
unattended for long

Steps in Programming the MPU AXI Module
Figure 5-1 Programmer’s Flowchart
1.
2.
No
Yes
3.
4.
5.
Take corrective action
Clear the NMI
System reset
Read module ID and configure MPU AXI
Program the MPUXm_NMIEN:NMIEN
Wait/poll for MPU AXI
Non-Maskable Interrupt
NMI is set?
Read the transaction information